Massachusetts Institute of Technology (MIT) scientists have engineered a 3D endometrial microenvironment by developing a tissue-inspired synthetic extracellular matrix (ECM) for human endometrial cells. This model simulates key aspects of the human menstrual cycle and introduces a synthetic platform for studying cell-cell and cell-matrix communication in a controlled, long-term, and tunable environment that will help understand the mechanisms that govern human menstrual health and disease.

The research article, “Organoid co-culture model of the cycling human endometrium in a fully synthetic extracellular matrix enables the study of epithelial-stromal crosstalk” was published in the Cell Press journal Med.

Tissue engineering a 3D endometrial microenvironment

In the endometrium, sex hormones drive fast tissue growth and maturation along with equally dynamic changes in ECM interactions with cells that are molecularly and mechanically associated with reproductive function. This is an amazing example of regenerative biology in action. These extraordinary regenerative qualities also play a role in common crippling illnesses like endometriosis, for which there is an urgent need for new treatments.

The stroma and epithelium cell populations play a major role in mediating sex hormone signals during the human menstrual cycle. However, the lack of models that allow for their study has hampered the field’s advancement. In this work, researchers at MIT synthesized a novel ECM to enable parallel studies of stromal cells and endometrial epithelial organoids.

Co-lead authors Juan Gnecco, PhD, now an assistant professor in the department of biomedical engineering at Tufts, and Alexander Brown, PhD, did this by analyzing the matrix composition and menstrual cycle-dependent endometrial integrin expression to find potential cell-matrix interaction cues for incorporating into a polyethylene glycol (PEG)-based hydrogel crosslinked with peptides that are labile to matrix metalloproteinase. Then, they looked for biophysical and molecular characteristics of the endometrium to figure out what kinds of mixtures would work for hormone-driven growth and differentiation of epithelial organoids, stromal cells, and co-cultures of the two types of cells. When co-encapsulated in hydrogels tuned to a stiffness regime similar to the native tissue and functionalized with two peptides, a collagen-derived adhesion peptide (GFOGER) and a fibronectin-derived peptide (PHSRN-K-RGD), each cell type showed characteristic morphological and molecular responses to hormone changes.

As a proof-of-concept, they then used this model to show how the hormone-dependent behaviors of the endometrial epithelium in co-culture with stroma are different from those in monoculture. For example, they saw that the pro-inflammatory cue IL1B seems to drive endometrial co-cultures, but not monocultures, to a state that mimics the symptoms of diseases like endometriosis.

The advantages of PEG for synthetic ECMs

This model makes it possible to study endometrial epithelial-stromal crosstalk’s molecular and phenotypic effects in long-term cultures of patient-derived endometrial cells. This is done by defining a completely synthetic ECM hydrogel designed to replace Matrigel for organoid culture and support stromal culture simultaneously. Natural matrices such as Matrigel and collagen—which have been used either alone for co-culture or combined creatively—include many extraneous signaling molecules that may drown out the signals produced by the cells they support. The main constituent of this synthetic ECM, PEG, is a blank slate known for its relative lack of interaction with proteins. Thus, GFs, cytokines, and other molecules produced by each cell type can freely dominate the cell-cell communication networks. By design, the synthetic ECM has only a small number of biological signals: two integrin ligands, two ECM-binding proteins, and a peptide crosslinker.

Even though this is just the first step in describing the synthetic ECM, it may be better than ECM-free co-culture models for mimicking and studying certain aspects of endometrial diseases.

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